ArcAdiAThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.http://dspace-roma3.caspur.it:802016-12-09T13:25:05Z2016-12-09T13:25:05ZReduction in the field-dependent microwave surface resistance inYBa2Cu3O7-delta with submicrometric BaZrO3 inclusions as a function of BaZrO3 concentrationPompeo, NicolaRogai, RaffaellaAugieri, A.Galluzzi, V.Celentano, G.Silva, Enricohttp://hdl.handle.net/2307/3802011-12-22T13:34:56Z2009-01-14T23:00:00Z<Title>Reduction in the field-dependent microwave surface resistance inYBa2Cu3O7-delta with submicrometric BaZrO3 inclusions as a function of BaZrO3 concentration</Title>
<Authors>Pompeo, Nicola; Rogai, Raffaella; Augieri, A.; Galluzzi, V.; Celentano, G.; Silva, Enrico</Authors>
<Issue Date>2009-01-15</Issue Date>
<Is part of>Journal of applied physics</Is part of>
<Volume>105</Volume>
<Pages>013927-013927-7</Pages>
<Abstract>In order to study the vortex pinning determined by artificiallyintroduced pinning centers in the small-vortex displacement regime, wemeasured the microwave surface impedance at 47.7 GHz in the mixed stateof YBa2Cu3O7-delta thin films, where submicrometric BaZrO3 particleshave been incorporated. As a function of the BaZrO3 content, weobserved that the absolute losses slightly decrease up to a BaZrO3content of 5%, and then increase. We found that themagnetic-field-induced losses behave differently in that they are notmonotonic with increasing BaZrO3 concentration. At small concentration(2.5%) the field-induced losses increase, but large reduction in thelosses themselves, by factors up to 3, is observed upon furtherincreasing the BaZrO3 concentration in the target up to 7%. Usingmeasurements of both surface resistance and surface reactance, weestimate vortex pinning-related parameters. We found that BaZrO3inclusions introduce deep and steep pinning wells. In particular, theminimum height of the energy barrier for single vortices is raised. Atlarger BaZrO3 content (5% and 7%) the phenomenon is at its maximum, butit is unclear whether it shows a saturation or not, leaving room forfurther improvements. (C) 2009 American Institute of Physics. [DOI:10.1063/1.3056179]</Abstract>2009-01-14T23:00:00ZEffect of BaZrO3 Inclusions on the Microwave Surface Impedance of YBCOFilms in a Magnetic FieldPompeo, NicolaRogai, RaffaellaGalluzzi, ValentinaAugieri, AndreaCelentano, GiuseppeCiontea, LeliaPetrisor, TraianSilva, Enricohttp://hdl.handle.net/2307/3822011-12-22T13:34:56Z2009-07-14T22:00:00Z<Title>Effect of BaZrO3 Inclusions on the Microwave Surface Impedance of YBCOFilms in a Magnetic Field</Title>
<Authors>Pompeo, Nicola; Rogai, Raffaella; Galluzzi, Valentina; Augieri, Andrea; Celentano, Giuseppe; Ciontea, Lelia; Petrisor, Traian; Silva, Enrico</Authors>
<Issue Date>2009-07-15</Issue Date>
<Is part of>IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY</Is part of>
<Volume>19</Volume>
<Pages>2917-2920</Pages>
<Abstract>We perform measurements of high-frequency (similar to 48 GHz) microwavesurface impedance with an applied magnetic field in YBa2Cu3O7-delta (YBCO) laser-ablated films with various amounts of BaZrO3 ( BZO)sub-micrometric inclusions, up to 7 mol % concentration. BZO inclusionsare very effective in the reduction of the field-induced surfaceresistance in our experimentally accessible field range [ 0, 0.8] T. Attemperatures low enough, the application of a moderate (similar to 0.2T) field makes the YBCO/BZO films markedly less dissipative than pureYBCO. This result, examined in the light of the very high measuringfrequency ( very small vortex oscillation amplitude) shows that BZOinclusions are even more effective pinning centers than columnardefects. We study the dependence of the vortex parameters ( vortexviscosity, pinning constant) on the BZO concentration. We examine thecorrelation between the reduction of the microwave dissipation and theareal density of BZO-induced defects. We argue that the very improvedperformances in a magnetic field are due to individual pinning ofvortices on BZO inclusions.</Abstract>2009-07-14T22:00:00ZTransport Property Improvement by Means of BZO Inclusions in PLD GrownYBCO Thin FilmsAugieri, AndreaGalluzzi, ValentinaCelentano, GiuseppeAngrisani, Achille ArmenioMancini, AntonellaRufoloni, AlessandroVannozzi, AngeloSilva, EnricoPompeo, NicolaPetrisor, TraianCiontea, LeliaGambardella, UmbertoRubanov, Sergeyhttp://hdl.handle.net/2307/3812011-12-22T13:34:56Z2009-06-04T22:00:00Z<Title>Transport Property Improvement by Means of BZO Inclusions in PLD GrownYBCO Thin Films</Title>
<Authors>Augieri, Andrea; Galluzzi, Valentina; Celentano, Giuseppe; Angrisani, Achille Armenio; Mancini, Antonella; Rufoloni, Alessandro; Vannozzi, Angelo; Silva, Enrico; Pompeo, Nicola; Petrisor, Traian; Ciontea, Lelia; Gambardella, Umberto; Rubanov, Sergey</Authors>
<Issue Date>2009-06-05</Issue Date>
<Is part of>IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY</Is part of>
<Volume>19</Volume>
<Pages>3399-3402</Pages>
<Abstract>A detailed study on YBa2Cu3O7-delta (YBCO) films with BaZrO3 (BZO)inclusions (YBCO-BZO) deposited on SrTiO3 substrate with different BZOcontents is presented. X ray diffraction, SEM imaging andsuperconductive critical temperature (T-c) measurements were performedto evaluate film growth quality. Independently from the BZO content,all YBCO-BZO films showed T-c values close to that of pure YBCOindicating that the T-c reduction which is usually observed on YBCO-BZOfilms can be successfully recovered by changing the depositionconditions. All YBCO-BZO films showed an improved critical currentdensity (J(c)) dependence on magnetic field if compared to the typicalJ(c)(H) of YBCO, resulting in higher irreversibility fields up to 9 Tat 77 K. SEM observation on etched samples suggests a direct linkbetween the defect density measured in YBCO-BZO samples and thatcalculated from the observed in field performances. The analysis ofJ(c)(B) as a function of applied magnetic field direction revealed thatthe pinning due to isotropic pinning centers typical for YBCO iscoupled with a c-axis correlated pinning in YBCO-BZO which can beascribed to BZO induced columnar defects. J(c)(B) recorded at severaltemperatures down to 10 K revealed matching effect features.</Abstract>2009-06-04T22:00:00ZNonlinear c-axis transport in Bi2Sr2CaCu2O8+delta from two-barrier tunnelingGiura, MaurizioPompeo, NicolaSilva, Enricohttp://hdl.handle.net/2307/3762011-12-22T13:34:56Z2009-03-31T22:00:00Z<Title>Nonlinear c-axis transport in Bi2Sr2CaCu2O8+delta from two-barrier tunneling</Title>
<Authors>Giura, Maurizio; Pompeo, Nicola; Silva, Enrico</Authors>
<Issue Date>2009-04-01</Issue Date>
<Is part of>Physical Review B</Is part of>
<Volume>79</Volume>
<Pages>144504</Pages>
<Abstract>Motivated by the peculiar features observed through intrinsic tunneling spectroscopy of Bi2Sr2CaCu2O8+delta mesas in the normal state, we have extended the normal-state two-barrier model for the c-axis transport [M. Giura , Phys. Rev. B 68, 134505 (2003)] to the analysis of dI/dV curves. We have found that the purely normal-state model reproduces all the following experimental features: (a) the parabolic V dependence of dI/dV in the high-T region (above the conventional pseudogap temperature), (b) the emergence and the nearly voltage-independent position of the "humps" from this parabolic behavior by lowering the temperature, and (c) the crossing of the absolute dI/dV curves at a characteristic voltage V-x. Our findings indicate that conventional tunneling can be at the origin of most of the uncommon features of the c-axis transport in Bi2Sr2CaCu2O8+delta. We have compared our calculations to experimental data taken in severely underdoped and slightly underdoped Bi2Sr2CaCu2O8+delta small mesas. We have found good agreement between the data and the calculations, without any shift of the calculated dI/dV on the vertical scale. In particular, in the normal state (above T-*) simple tunneling reproduces the experimentaldI/dV quantitatively. Below T-* quantitative discrepancies are limited to a simple rescaling of the voltage in the theoretical curves by a factor similar to 2. The need for such modifications remains an open question, that might be connected to a change of the charge of a fraction of the carriers across the pseudogap opening.</Abstract>2009-03-31T22:00:00Z